The present invention is direct to a dental x-ray diagnostics installation having a source of x-radiation and a holder for a film cassette with the source of x-radiation having a diaphragm for limiting the x-ray beam, which diaphragm is interchangeably held for the purpose of changing the diaphragm opening for different film cassette formats.
In panorama x-ray diagnostics installations with which slice exposures of the jaw of a patient can be produced, there is frequently the possibility of being able to produce exposures of the entire skull of a patient, which exposures are referred to as ceph exposures, with the assistance of an additional, adaptable head holder. Given a change from slice exposure to ceph exposure, it is necessary, for reasons of radiation protection, to limit the width or shape of the x-ray beam of the primary diaphragm to the cassette format. To this end, a known apparatus sold under the trademark "ORTHOPANTOMOGRAPH 10" has a unit sold under the trademark "ORTHOCEPH 10", and is provided with two primary diaphragms provided with different diaphragm openings for slice exposures on the one hand and for ceph exposures on the other hand. These primary diaphragms have to be interchanged when a switch is made from a slice exposure to a ceph exposure and vice versa.
Over and above the possibility of being able to alternatively select between slice exposure and ceph exposure, there is also a desire to be able to expose regions of the subject which differ in size, for example, portions of the skull or of the jaw. To this end, it can be appropriate to change the cassette format and to limit the radiation beam to the selected format for reasons of radiation protection.